My terminal sparks when connecting to a battery post

Written by kurt schanaman
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My terminal sparks when connecting to a battery post
Automotive batteries can present an explosion hazard if flames or sparks come into contact with dangerous hydrogen gas collected near the top of the battery. (dead battery image by Katrina Miller from

Automotive batteries can be dangerous to work around. Such batteries contain a "wet" chemical reactor where electricity is stored. Due to its chemical composition, the reactor generates hydrogen gas that can collect along the top of the battery, creating a potential for explosion if ignited. Clean battery terminals can reduce the amount of hydrogen around the top of the battery, and correct removal and replacement of the terminals will prevent unsafe sparks.

Skill level:

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Things you need

  • Protective eye goggles
  • Long-sleeve shirt
  • Leather cloves
  • Combination battery terminal and post cleaner
  • 354ml. jar of water
  • Baking soda

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  1. 1

    Put on protective eye goggles, a long-sleeve shirt and leather gloves to reduce the chances of personal injury while working on any automotive battery.

  2. 2

    Remove the black negative battery cable first, and secure it in a location where the cable clamp will not come into contact with metal or the positive post of the battery.

  3. 3

    Remove the red positive battery terminal last, and secure it in a location where it will not come into contact with either of the battery posts.

  4. 4

    Place 3 or 4 tbsp of baking soda into 354ml. of water. Gently pour this solution over one battery post at a time and wait for the solution to begin bubbling as it neutralises any corrosive acid accumulation on and around the post. Use a wire battery-post brush to brush away the neutralised material, then flush the area with baking soda solution until there is no longer any foaming action. Perform this same cleansing step for the other battery post and for both terminals.

  5. 5

    Reconnect the terminals to the battery posts by connecting the red positive battery terminal first, making sure the negative terminal isn't touching any metal of the vehicle. Tighten the positive terminal until just slightly more than hand-tight, then connect the black negative battery terminal to the negative post of the battery, tightening it just more than hand-tight.

Tips and warnings

  • To prevent sparks, always remove the black negative terminal first when removing the terminals, and install that negative terminal last when reinstalling.
  • Always allow proper ventilation of the battery when removing and installing battery terminals to battery posts. Lift the bonnet of the vehicle and allow the air to circulate for several minutes before you begin working to ensure any hydrogen gas has ample time to dissipate.
  • Never smoke cigarettes or use a cigarette lighter near a car battery. Explosion may result in serious injury or fatality.

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